How to catch MongoNetworkError: connect ECONNREFUSED in Node when using mongoose.createConnection()

[intersides]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Mongoose version

8.0.0

Node.js version

21

MongoDB server version

5.0

Typescript version (if applicable)

No response

Description

on a lost connection there is no clear way to trap MongoServerSelectionError: connect ECONNREFUSED 127.0.0.1:27017
thrown from: node_modules/mongodb/lib/sdam/topology.js:276:34

The connection is created as

try{
  mongooseConnection = mongoose.createConnection(mongoUri, {
      serverSelectionTimeoutMS: 5000
  });
       ....
}
 catch(e){
    console.error(e);
}

Steps to Reproduce

• create a database connection with a mongo instance that can be shut down at will. After connection all the relative callbacks are triggered (connected, open, etc..).
• shut down the mongo db database.
• callbacks are triggered (disconnect). connection.readystate changes to 0.
• wait into this dosconnected mode for about 10 seconds

The following appears:
MongoNetworkError: connection 1 to 192.168.32.2:27017 closed
at Connection.onClose (/opt/backend/node_modules/mongodb/lib/cmap/connection.js:124:28)
at Socket. (/opt/backend/node_modules/mongodb/lib/cmap/connection.js:66:46)
at Socket.emit (node:events:519:28)
at TCP. (node:net:337:12) {
[Symbol(errorLabels)]: Set(0) {},
[cause]: undefined

After 2 more seconds the disconnect callback is triggered and the following appear:

MongoServerSelectionError: connect ECONNREFUSED 127.0.0.1:27017
backend | 13:31:20 0|main | at EventTarget. (/opt/backend/node_modules/mongodb/lib/sdam/topology.js:276:34)
backend | 13:31:20 0|main | at [nodejs.internal.kHybridDispatch] (node:internal/event_target:822:20)
backend | 13:31:20 0|main | at EventTarget.dispatchEvent (node:internal/event_target:757:26)
backend | 13:31:20 0|main | at abortSignal (node:internal/abort_controller:374:10)
backend | 13:31:20 0|main | at TimeoutController.abort (node:internal/abort_controller:396:5)
backend | 13:31:20 0|main | at Timeout. (/opt/backend/node_modules/mongodb/lib/utils.js:1011:92)
backend | 13:31:20 0|main | at listOnTimeout (node:internal/timers:573:17)
backend | 13:31:20 0|main | at process.processTimers (node:internal/timers:514:7) {
backend | 13:31:20 0|main | reason: TopologyDescription {
backend | 13:31:20 0|main | type: 'Unknown',
backend | 13:31:20 0|main | servers: Map(1) { 'mongo1:27017' => [ServerDescription] },
backend | 13:31:20 0|main | stale: false,
backend | 13:31:20 0|main | compatible: true,
backend | 13:31:20 0|main | heartbeatFrequencyMS: 10000,
backend | 13:31:20 0|main | localThresholdMS: 15,
backend | 13:31:20 0|main | setName: null,
backend | 13:31:20 0|main | maxElectionId: null,
backend | 13:31:20 0|main | maxSetVersion: null,
backend | 13:31:20 0|main | commonWireVersion: 0,
backend | 13:31:20 0|main | logicalSessionTimeoutMinutes: null
backend | 13:31:20 0|main | },
backend | 13:31:20 0|main | code: undefined,
backend | 13:31:20 0|main | [Symbol(errorLabels)]: Set(0) {},
backend | 13:31:20 0|main | [cause]: MongoNetworkError: connect ECONNREFUSED 127.0.0.1:27017
backend | 13:31:20 0|main | at connectionFailureError (/opt/backend/node_modules/mongodb/lib/cmap/connect.js:379:20)
backend | 13:31:20 0|main | at Socket. (/opt/backend/node_modules/mongodb/lib/cmap/connect.js:285:22)
at Object.onceWrapper (node:events:634:26)
at Socket.emit (node:events:519:28)
at emitErrorNT (node:internal/streams/destroy:169:8)
at emitErrorCloseNT (node:internal/streams/destroy:128:3)
at process.processTicksAndRejections (node:internal/process/task_queues:82:21) {
[Symbol(errorLabels)]: Set(1) { 'ResetPool' },
[cause]: Error: connect ECONNREFUSED 127.0.0.1:27017
at TCPConnectWrap.afterConnect [as oncomplete] (node:net:1605:16) {
errno: -111,
code: 'ECONNREFUSED',
syscall: 'connect',
address: '127.0.0.1',
port: 27017
}
}
}

Expected Behavior

try{
mongooseConnection = mongoose.createConnection(mongoUri, {
serverSelectionTimeoutMS: 5000
});
....
}
catch(e){
console.error(e);
}

The Error should have been reported in the catch block

[IslandRhythms]

Try adding .catch(e => console.log(e)) to the create connection code instead of wrapping it in a try catch and see if that helps.

[intersides]

No, also asPromise() the mongoose.createConnection the catch doesn't get called.

mongoose.createConnection(params.url, { serverSelectionTimeoutMS: 5000 }).asPromise() .then(_connection=>{ ... }) .catch(e => console.log(e));

[vkarpov15]

Once initial connection is completed, await mongoose.createConnection().asPromise() will not throw an error if the connection is later interrupted.

Given that you aren't properly handling errors in your original post (missing await and asPromise() with createConnection()), the issue is most likely that you aren't correctly handling errors in other parts of your code as well. For example, the following code will throw an uncaught error if the MongoDB server stops:

try {
  TestModel.findOne();
} catch (err) {
  handleError(err);
}

TestModel.findOne() is an asynchronous operation and returns a thenable, try/catch won't catch errors unless you await as follows

try {
  await TestModel.findOne();
} catch (err) {
  handleError(err);
}

[github-actions]

This issue is stale because it has been open 14 days with no activity. Remove stale label or comment or this will be closed in 5 days

[github-actions]

This issue was closed because it has been inactive for 19 days and has been marked as stale.

[sadeghhosseini]

This might help:

process.on('unhandledRejection', (error) => {
        if (error instanceof mongoose.mongo.MongoNetworkError) {
            console.log(error);
        } else {
	    console.log('unhandled rejection: ', error);
	    throw new Error(); // so that other types of unhandled exceptions crash the server!
        }
    });